Method of utilizing aluminum skimmings and analogous material.



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@FFKQE -JAIIES WEIGHT LAWBIE, O33 ILEILWAUKEE, WISCONSIN, ASSIGNOR, BY MESH E ASSIGN- E'IENTS, "0 WILLIAM; F. JQBBINS, INCORPORATED, OF AURORA, ILLINOIS, A CORPO- RATION 6F ILLINUIS.

ME'I'HQD 0F 'UIDILIZING ALUMINUM SKIMMIN GS AND ANALOGOUS MATERIAL.

12' b all whom it may concern:

Be it known that 1, James WV RIGHT LAW- am, a citizen of the United States, residing at li lilwaukee, in the county of Milwaukee and Etate of Wisconsin, have invented new and useful Improvements in Methods of Utilizing Aluminum Skimmings and Analogous Materials, of which the following is a full, clear, concise, and exact description.

This invention. relates to a process of treating aluminum skimmings, screenings, dross, slags or analogous aluminous materials for the purpose of producing therefrom certain valuable and useful products.

In carrying out my invention I prefer the following procedure. From the skimmings or analogous materials the larger amounts of free aluminum or its alloys are separated, if desired, by suitable means. This treatment leaves a residue consisting chiefly of the oxid, the carbids and the nitride of aluminum, and

contains also the following: compounds of iron, of copper and of zinc, and free carbon in relatively large amounts; free, finely di vided aluminum and its alloys and other free metals in smaller amounts; and varying proportions of soluble salts and other impurities. This residue is treated for the production of pure alumina by method somewhat similar to those hitherto employed for the manufacture of this product from bauxite and other aluminabearing minerals or nitrids of aluminum obtained from these minerals, but differing from these methods in order to avoid the ditficulties in treatment due to the impurities found in these skimmings or analogous materials, which impurities are not contained in the other sources of alumina above mentioned, and to utilize as completely as possible those substances contained as impurities but from which valuable products can be obtained. Since this raw material herein described varies as it is obtained from different sources and at difierent times, the process is sufficiently elastic to be adaptable to all matefials obtained, as will be shown herein.

The residue described above may, after 'crushing, if necessary, or otherwise reducing to a suitable degree of fineness. be washed with water to remove the soluble salts, but if it contains a large proportion of nitrids easily decomposed by water this washing may be omitted.

Specification of Letters Patent.

The next step in the process is the preparation of a solution of an aluminate lye by one of the two vfollowing methods: (1) by treating the material, suitably prepared as described above, with a solution of an alkaline caustic, preferably sodium hydroxid, or (2) by fusion with an alkaline carbonate or an alkaline hydroxid and subsequently leaching the fused mass with water.

If the former'method of preparing the solution is employed, the following points are to be considered: It is well known that the oxid (and possibly also the nitrids) of aluminum can exist in several modifications diifering widely in ease of solubility in acids or alkalis. In the materials from which pure alumina is ordinarily manufactured, such as bauxite and other minerals. the aluminum is in the form of a diiticultly soluble aluminum oxid, probably hydrated,

since all of these minerals contain a relaor with the application of but little heat be".

yond that developed by the reaction, and without the application of pressure or with the application of but little pressure beyond that developed as a result of the evolution of gases (ammonia, hydrogen, hydrocarbons, etc.) during the course of the reaction. But, owing perhaps to a previous exposure to an unusually hightemperature in the melting processes from which these materials are originally obtained, part of the oxids and of the nitrids is more diiiicultly soluble, and heating, under pressure, is resorted to in order to dissolve all of the available aluminous content of the material. For the same reason also, considerable variation in the concentrations and the relative amounts of the caustic alkaline solution used in dissolving the aluminous content of the material is allowable and advisable. In general terms, the amounts and concentrations should be so chosen that hydrated alumina can be precipitated without too much dilution.

Patented Apr. 9, 1918.

Application filed April 8, 1913. Serial No. 759,645.

The second point to be considered in the 7 preparing the aluminate solution must be constructed so as to allow of the escape of the gases in such a way that the ammonia may subsequently be separated from the othergaseous products. It is evident, as

has been mentioned above, that the pressure produced by the evolution of the gases may be taken advantage of in the process of making the aluminate solution. The ammonia in acids for the evolved may be finally absorbed in water for the production of aqueous ammonia, or production of ammonium salts.

If the second process for making the aluminate lye is employed, the quantities of alkali and the apparatus for the leaching mustbe chosen with a view to the same considerations as those mentioned above.

Tothe solution of the aluminate lye, either before or during the process of producing it, as described,.varying amounts of sulfur or of alkaline sulfid or of other sulfids are added to prevent the contamination of the solution by zinc, or copper or lead, or to remove them if they are already present in the solution. Since alkaline solutions may be thus contaminated by zincand lead, un-

' less the zinc and lead are removed they rapidly use up the alkali and prevent its repeated use, or may be precipitated from the solution, thus contaminating the alumina obtained from this solution. Copper is caused to go into the alkaline solution apparently by. the formation of an organic ammonia derivative. which is relatively stable but which can be decomposed and from which the copper can be precipitated in the manner described. The, solution of copper does not. always occur. It is clear that the treatment'just described does not only prevent the contamination of the solution by copper, zinc and lead, but it has the added advantage of leaving these substances in the residue in a form in which they are very easily extracted and converted into useful products. Furthermore, the treatment would remove from the solution any other metals whose sultids can be precipitated from alkaline solutions. While this is the process preferred for removing the impurities above mentioned, any other precipitation method may be employed.

After the treatment with the alkaline materials as described above has been continued until practically all of the aluminous conmeaoea tent (oxid, nitrids, carbids and free metal) ha been dissolved, the resultin aluminate lye solution is separated from t e insoluble residue by suitable means, preferably by filforms the subject matter of my Patent No.

1,128,119, granted May 29, 1917.

The aluminate solution, freed from copper and zinc and other impurities as described above, is treated for the precipitation of alumina by various means, such as vigorous stirring, inoculating with crystallized hydrated alumina, or by passing carbon dioxid through the solution. But any other method for the precipitation of the alumina may be employed. Or th.v solution may first be concentrated or diluted and the alumina then be precipitated. The precipitated alumina is then separated from the remaining solution by suitable means and washed. It may then be dried and ignited to make non-hygroscopic alumina which may be used in various ways. Or the alumina may be used without drying for the production of iron-free aluminum sulfate by well known means, or for other purposes.

The solution from which the alumina or most of the alumina has been precipitated and removed may be used for dissolving further portions of the original materials, or it may be concentrated and then so used. 'But since some of the material which is to be treated, as has been described, contains fairly large roportions of carbonate, or since carbon ioxid may have been used in the precipitation of the alumina, some, or if carbon dioxid has been used a large proportion, of the caustic alkali will have been converted into carbonate and will therefore be useless in dissolving further portions of the material. The solution may therefore be treated with calcium oxid or calcium hydroxid before it is used to dissolve further portions of the skimmings and analogous materials as herein mentioned. This treatment will'regenerate the alkali in the solution and will at the same time cause the precipitation of calcium carbonate admixed with calcium aluminate, if any alumina has been left in the solution. In those cases where the precipitate thus formed contains appreciable amounts of aluminum this may be regained as aluminum sulfate by treating the precipitate with sulfuric acid and filtering from the remaining calcium sulfate.

Although the procedure herein described is the one preferred, various changes may be made to produce the same results without. departing from the spirit of the intention. Thus, for instance, if itis desired to separate the main portion of the copper from the zinc at the outset, the sulfur or sullids may be added after the aluminate lye solution has been separated from the residue containing most of the copper. Thus the zinc will be precipitated as almost pure zinc sultid ,and the copper will be left behind in the residue, with other compounds from which it can readily be separated. ()r, in case that very little zinc is contained in the skimmings and analogous n'iaterials as here in mentioned. which rarely occurs. the treat mentwith sult'ur or sultiils may be omitted. Likewise the preliminary steps of the re moral of the larger amounts of tree metal. as well as the crushing, may not always be needed and can therefore be omitted.

By the term pure alumina as it is used in the claims and the specification, 1 mean the alumina as it is obtained by precipitation from the solutions herein described, and do not. wish to imply that the alumina is necessarily tree from all minor contamination.

llaving thus described my invention, what I claim as new and desire to secure by Letters- Patent is- 1. The method of utilizing aluminum skimmings, slags, dross or analogous waste aluminous materials, which consists in treating the materials to form an aluminate solution, pre ipitating as sultids the zinc, copper and other impurities from the aluminate solution, separating the solut on from the solids, precipitating pure alumina from the purified aluminate solution, sepa'ating the precipitated alumina from the remaining solution, and collecting and washing the pure alumina.

2. The method ,of utilizing aluminum skimmings, slags, dross or analogous waste aluminous materials. which consists in treating the waste materials with a solution of alkaline caustic. precipitating as sultids the zinc, copper and other impurities from the alun'iinate solution, separating the solution from the solids. precipitating pure alumina from the purified aluminate solution. separating the precipitated alumina from the remaining solution, and collecting and wash ing the pure alumina.

3. The method of utilizing aluminum skimmings, slags. dross or analogous waste aluminous u'iaterials. which consists in treating the waste materials to form an alumi nate solution, precipi ating as sulfids the zinc, copper and other impurities from the aluminate solution, and separating the solution .from the solids, consisting in part. of compounds of copper, of zinc and of iron or any of them.

4. The method of utilizing aluminum skimmings, slags, d ss or analogous waste aluminous materials, which consists in treating the waste materials with a solution of alkaline caustic, precipitating as sulfids the zinc, coppe' and other impurities from tho aluminate solution. and separating the solution from the solids, consisting in part of compounds of copper, of zinc and of iron or any of them.

5. The method of utilizing aluminum skinnuings, slags, dross or analogous waste aluminous materials, which consists in treating the materials to form an aluminate solution, n-ecipitating the zinc, copper and other impurities from the aluminate solution, separating the solution from the solids, precipitating pure alumina from the purified aluminate solution, separating the precipitated alumina from the remaining solution, and collecting and washing the pure alumina.

t'. The method of utilizing aluminum skimmings, slags, dross or analogous waste aluminous materials, which consists in treating the waste materials with a solution of alkaline caustic, precipitating the zinc, copper and other impurities from the aluminate solution, separating the solution from the solids, precipitating pure alumina from the purified aluminate solution, separating the precipitated alumina from the remaining solution, and collecting and washing the pure alumina.

7. The method of utilizing aluminum skimmings, shws, dross or analogous waste ahuninous materials, which consists in treating the 'aste materials to form an aluminate solution, precipitating the zinc, copper and other impurities from the aluminate solution. and separating the solution from the solids, consisting in part of compounds of copper. of zinc and of iron or any of them.

8. The method of utilizing aluminum skimmings, slags, dross or analogous waste aluminous materials, which consists in treating the waste materials with a solution of alkaline caustic, precipitating the zinc, cop- 1)( and other impurities from the'aluminate solution, and separating the solution from the solids, consisting in part of compounds of copper, of zinc and of iron or any of them.

Tn witness whereof, I have hereunto subscribed my name in the presence of two witncsses.

JAMES WRIGHT LAVVRIE. lVitnesses:

FRANK J. STERN, Hnmnxu J. SCIILESINGER. 

